Time-Domain Digital-Coding Active Frequency Selective Surface Absorber/Reflector and Its Imaging Characteristics

Switchable active frequency selective surface (AFSS) absorber/reflector can work in opposite scattering state and be widely applied in the stealth field. At present, abundant researches on material design have been conducted to obtain excellent electromagnetic (EM) properties. However, there are few studies on the modulation effect of switchable AFSS absorber/reflector on the EM wave. In this article, a time-domain digital-coding AFSS absorber/reflector is proposed to manipulate the spectral distribution of harmonic. The accurate control of each harmonic is achieved through AFSS modulating parameters. Then, a simple controller based on FPGA is designed. By coding “0” and “1” elements with controlled sequences, the AFSS can be switched flexibly in both absorbing and reflection states. On this basis, the imaging characteristics of time-domain digital-coding AFSS absorber/reflector are further analyzed, and distance transformation phenomena are described in detail. The synthetic aperture radar (SAR) experiments are performed to demonstrate the required function of distance transformation.